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Anatomy - Embryology (Abdomen)
SUNY Upstate College of Medicine Class of 2015
36
Anatomy
Graduate
09/29/2011

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Cards

Term
Primary gut tube/primordial gut
Definition

-endoderm from original yolk sac

-will form epithelial lining of digestive tract and the structures derived from it

Term
Oropharyngeal membrane
Definition
cranial end gastrointestinal tract
Term
cloacal membrane
Definition
caudal end of gastrointestinal tract
Term
splanchnopleuric mesoderm
Definition
forms the dorsal mesentery and the visceral peritoneum
Term
somatopleuric mesoderm
Definition
forms the parietal peritoneum
Term
dorsal mesentery
Definition

-initially suspends the foregut, midgut and hindgut

-begins at caudal extend of esophagus, continues to hindgut

Term
ventral mesentery
Definition

-less extensive

-derived from septum transversum

-anchors lower end of esophagus, stomach, and 1st part of duodenum to the anterior body wall

Term
peritoneum
Definition
double layers of peritoneum (from mesoderm) for the mesenteries
Term
esophagus development
Definition

-originates from the foregut immediately posterior to the pharynx

-at 4 weeks, the lung buds evaginate from the ventral surface of the forming esophagus

-it is then separated from the forgut by the tracheoesophageal septum

-by 8 weeks, endodermal epithelal cells proliferate and obliterate lumen of esophagus

-recanilization of this segment is accompanied by changes in its epithelial lining

Term
congenital defects associated w/ the esophagus
Definition

-tracheoesophageal fistula or esophageal atresia: defect in formation of tracheoesophageal septum

-if recanilization fails to occur, esophageal atresia or stenosis occurs: prevents embryo from swallowing normal amount of amniotic fluid, resulting in polyhydramnios (excess fluid in amniotic sac)

Term
greater curvature stomach
Definition
-comes from the dorsal aspect of the foregut which grows more rapidly than the ventral portion
Term
lesser curvature stomach
Definition
- comes from the ventral foregut
Term
rotation of the stomach
Definition

- develops as spindle shaped enlargement of the forgut during the 4th week --> originally lies in median plan but due to differnetial growth patterns and rotation, its position and overall shape undergo dramatic changes

-rotation results in pulling the dorsal mesentery to the left

-as it grows, the mesentery balllons out to form the lesser sac, etc.

Term
omental bursa "lesser sac"
Definition

- develops from the ballooning out of the dorsal mesentery

-defined space behind the stomach

Term
greater omentum
Definition

-forms from the growth of the dorsal mesentery and the omental bursa

-bi-layered pouch attached to greater curvature of the stomach

-eventually the posterior layer fuses w/ the mesentery of the transverse colon to form the transverse mesocolon and the space in the "pouch" of the greater omentum is obliterated

Term
lesser omentum
Definition

-formed from the ventral mesentery associated w/ the stomach

-runs b/w liver and stomach and 1st part of duodenum

-in adult it is subdivided into hepatogastric and hepatoduodenal ligaments

Term
falciform ligament
Definition

-forms from the ventral mesentery associated w/ the stomach

 

Term
hepatogastric/hepatoduodenal ligaments
Definition
-subdivision of the lesser omentum (ventral mesentery)
Term
duodenum
Definition

-develops from caugal foregut and cranial portion of the midgut as C-shaped, ventrally positioned loop

-rotates to the right w/ movement of the stomach

-due to repositioning during growth, the mesoduodenum fuses w/ the peritoneum covering the posterior body wall --> except for cap, duodenum is secondarily fixed

-recanilization usually complete by 8th week (epithelial cells of lining differentiate)

Term
congenital defects associated w/ the duodenum
Definition

-Duodenal stenosis (narrowing of lumen) or duodenal atresis (complete occlusion lumen) can occur if canalization is incomplete or absent

-infants with this defect initially exhibit polyhydramnios (begin vomiting shortly after birth)

Term
Liver
Definition

-endodermal cells from ventral surface of caudal foregut

-differentiate into liver bud and become invested in the ventral mesentery (from septum transversum)

-the ventral mesentery that cover the surface becomes visceral peritoneum

-primary hematopoetic organ, produces both RBC and WBC's as early as 6 weeks

Term
bare area of the liver
Definition

- at cranial aspect, liver is in direct contact w/ mesodermal cells that will become the central tendon of the diaphragm

-no peritoneal covering between liver and inferior diaphragm surface

Term
gall bladder
Definition

-endodermal outgrowth from ventral surface of caudal foregut

-cystic diverticulum first appears as small outpouching from proximal portion of hepatic diverticulum (liver bud)

-attached to hepatic duct via cystic duct (forms common bile duct)

-initially on ventral surface duodenum, after rotation the definitive common bile duct is on the dorsal aspect of this organ

Term
head and uncinate process of pancreas
Definition

-endodermal outgrowth from ventral surface of the caudal foregut

-due to rotation of the duodenum, ventral pancreatic bud is carried posteriorly and fuses w/ the larger dorsal bud to form the head and uncinate process

Term
neck, body and tail of pancreas
Definition

- endodermal outgrowths from the ventral surface of the caudal foregut

- arises from dorsal pancreatic bud which fuses with the smaller ventral bud

Term
main pancreatic duct
Definition

- originates from the ventral pancreatic bud

-maintains original association with bile duct to form hepatopancreatic ampulla

Term
hepatopancreatic ampulla
Definition
- leads into major duodenal pilla in 2nd part of duodenum
Term
Annular pancreas
Definition

- formed from presence and subsequient fusion fo a portion of an anomalous double (bifid) ventral pancreatic bud w/ the dorsal pancreatic bud

- a ring of pancreatic tissue that surrounds the duodenum, constricting and obstructing it

Term
Spleen
Definition

-mesoderman origin

-hematopoetic organ

-during 5th week it develops w/in dorsal mesentery

-due to rotation of stomach, left surface of mesentery fuses w/ peritoneum covering the developing left kidney

-in adult, spleen retains intraperitoneal location --> connected to body wall via splenorenal ligament

Term
physiological umbilical herniation of the primary intestinal loop
Definition

-for about 5 weeks, the intestinal tract develops outside of the body, protruding into the umbilical cord

 

Term
small intestines
Definition

-the cranial limb component of the primary intestinal loop grows into the distal part of the duodenum, jejunum, and part of the ileum

- elongating large intestine roates 90 degrees around the SMA (on the left)

-during 10th week intestines are restored to abdominal cavity, w/ small intestine returning first

 

Term
large intestines
Definition

-the caudal limb of the primary intestinal loop will develop into the cecum and appendix (from the caecal diverticulum)

- elongating large intestine roates 90 degrees around the SMA (on the left)

-during 10th week intestines restored to abdominal cavity, large intestine returns 2nd and undergoes 180 degree rotation, the cecum descends to lower right quadrant

Term
abnormal rotation of the midgut
Definition

-Nonrotation, reversed rotation, mixed rotation or malrotation: all involve disparate movements of small intestine that result in abnormal positioning of GI tract and associated mesenteries (most not life threatening)

-volvulus: propensity for gut to twist upon itself, portion of small bowel may become obstructed and the vascualr supply severely compromised

 

Term
meckel's diverticulum
Definition

-persistence of vitelline duct as a blind pouch, usually projects from distal ileum

-intestinal obstruction and gastrointestinal bleeding are potential complications

-occasionally a ligament may connect a meckel's diverticulum to the umbilicus

Term

development of hindgut

(1/2 transverse colon, descending and sigmoid colon, rectum, superior anal canal, epithelium urinary bladder and urethra)

Definition

- endoderm of hingut ends at cloaca, which is sealed by the cloacal membrane and then lined internally by endoderm and covered externally by ectoderm of anal pit

-6th week: urorectal septum separates cloaca into anterior urogenital sinus and posterior rectum and anal canal

-superior 2/3 anorectal canal forms from endoderm hingut, inferior 1/3 originates from ectoderm of anal pit

-junction b/w two regions marked by pectinate line (different vessels and nerves supply the anorectal canal on either side of it)

Term
Imperforate anus
Definition

-# of defects that relate to absence of an anal opening

-congenital persistence of anal membrane is amenable to straightforward surgical procedures

-atresia of anal canal/rectum is more difficult

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